1. Field of the Invention
The present invention relates to a method and system of determining overall well performance by the calculation of a well optimization index derived from a relation between well operation execution performance and the productivity of the well.
2. Description of the Related Art
In conventional systems, there is no single parameter in common use that allows operations groups to systematically assess the degree of success to which a well has been drilled or intervened.
Most parameters used today relate only to the particular area they are in, or are related to an Authorization for Expense (AFE) or plan generated by the executors themselves. Typically in oil companies today, a successful well is when the AFE targets for cost and time are achieved underbudget, or when these time or cost targets are improvements in the area of activity. Similarly for production targets, when historical rates are exceeded the well is considered a success. Clearly without comparisons to absolute or potential values, the true success or optimization of a well can not be concluded, and neither can any systematic cross-area comparisons be made.
Well optimization has two fundamental elements, well cost (or time), and well productivity. Typically parameters that express the performance in these two areas are kept separate, and as a consequence, it is not uncommon that very successful drilling performance is not mirrored in well productivity, or vice versa. At a minimum, it is commonly seen that the timing and degree of effort applied to each area is poorly synchronized.
Further, since in most projects, fundamental inputs to determine well optimization are not immediately available, and would require a significant effort to generate, achieving an understanding of optimum well times and production potential such that well optimization can be easily determined with a particular degree of accuracy, is necessary.
Methods and systems consistent with the present invention include the calculation of a common indicator for tracking trends and monitoring overall well performancexe2x80x94known as a well optimization index (WOI).
The WOI is calculated as a weighted average of two numbers reflecting operation execution performance (i.e., the Well Construction Operation Time Ratio (WCTR)) and production result performance (i.e., the Productivity Index Ratio (PIR)). The WOI is general for all kinds of well operations (i.e., oil or gas wells), such as drilling new wells or re-entering old wells, completions, workovers or rig-less work (i.e., stimulation, coiled tubing (CT), etc.).
The two indices WCTR and PIR each represent the performance of the well operation performed as compared to an optimum value. The WCTR can be calculated immediately after the well operation is completed, but the productivity index ratio PIR can only be calculated after the well production initiates and stabilizes. Because of this reason, the WOI index might not be available until a certain amount of data on the well operation is received.
Since production is typically of more ultimate value than the amount of cost that can be saved by reducing drilling or intervention times, the PIR term is weighted. Currently the proposed weighting is based upon xe2x80x9caveragexe2x80x9d global production values versus xe2x80x9caveragexe2x80x9d global well costs. The weighting is expressed as a constant, which represents recovery of cost.
In one embodiment, consistent with the present invention, the method of determining the WOI is carried out in a spreadsheet program used in a data-processing system, the program performing the method including the steps of generating a well construction time ratio WCTR for the well; generating a well productivity index ratio PIR for the well; and automatically generating a well optimization index WOI for the well based on a relation between the well construction time ratio WCTR and the well productivity index ratio PIR.
Specifically, in one embodiment consistent with the present invention, the WOI generating step includes automatically comparing a weighted average of an operation execution performance as defined by the well construction time ratio WCTR, to the production result performance as defined by the well productivity index ratio PIR, according to the following expression:       WOI    =                                        PI            R                    ⁢          N                +                  WCT          R                            N        +        1              ;
wherein N is a weighting constant which represents a recovery of cost of a well operation, that is estimated based on historical data. In another embodiment consistent with the present invention, the WOI comparing step includes the step of inputting the weighting constant N from either an external source or a memory storage device.
In another embodiment consistent with the present invention, the WOI generation step includes the step of receiving a name of the well from an external source prior to the well construction time ratio WCTR generating step. The well construction time ratio WCTR generating step includes the step of automatically comparing a well construction theoretical limit WCTL, defined as a theoretical minimum rig time to execute a well operation, in days, to an actual well construction time WCTL, in days, in accordance with the following expression:       W    ⁢          xe2x80x83        ⁢    C    ⁢          xe2x80x83        ⁢          T      R        =                    W        ⁢                  xe2x80x83                ⁢        C        ⁢                  xe2x80x83                ⁢                  T          L                            W        ⁢                  xe2x80x83                ⁢        C        ⁢                  xe2x80x83                ⁢                  T          A                      .  
In one embodiment consistent with the present invention, the well construction time ratio WCTR varies from 1.0 in a best case where intervention time equals said predetermined technical limit WCTL, to zero in a worst case, where intervention would not be completed.
In a further embodiment consistent with the present invention, the well construction theoretical limit WCTL is a predetermined technical limit for each well type, and the well construction theoretical limit WCTL is either retrieved from the memory storage device or received from an external source.
In another embodiment consistent with the present invention, the well construction theoretical limit WCTL is an addition of actual best time of historical data for each phase for each well type, minus fifteen percent, and the well construction theoretical limit WCTL is either retrieved from a memory storage device or received from an external source.
In a further embodiment consistent with the present invention, the WCTR comparing step includes the step of receiving the actual well construction time WCTA from either the external source or the memory storage device.
In another embodiment consistent with the present invention, when a different rig is used to complete the well, the well construction theoretical limit WCTL and the actual well construction time WCTA are each calculated by adding drilling rig days plus completion rig days for the well, and the calculated well construction theoretical limit WCTL and the calculated actual well construction time WCTA are received from either the external source or the memory storage device.
In another embodiment consistent with the present invention, when the technical limit WCTL is not available, then the well construction time ratio WCTR is replaced by an operation cost ratio OCR, as defined by the following expression:       O    ⁢          xe2x80x83        ⁢          C      R        =            O      ⁢              xe2x80x83            ⁢              C                  A          ⁢                      xe2x80x83                    ⁢          F          ⁢                      xe2x80x83                    ⁢          E                            O      ⁢              xe2x80x83            ⁢              C        A            
wherein:
OCAFE=Operational Cost as given by an Authorization For Expense
OCA=Actual Operation Cost; and
wherein when the OCAFE and the OCA are either retrieved from the memory storage or received from an external source, the OCR is automatically generated.
In another embodiment consistent with the present invention, the well productivity index ratio PIR generating step includes the step of automatically comparing an optimum productivity index PIO, in BFPD/psi (or BFPD/psi/foot of perforated interval), to an actual productivity index PIA, in BFPD/psi, in accordance with the following expression:
PIR=PIA/PIO. 
In another embodiment consistent with the present invention, the well productivity index ratio PIR varies from 1.0 in a best case where productivity of the well is at an optimum, and zero in a worst case, where the well has no production.
In one embodiment consistent with the present invention, the actual productivity index PIA is automatically generated in accordance with the following expression:       P    ⁢          xe2x80x83        ⁢          I      A        =            Q      a              (                        P                      a            ⁢                          xe2x80x83                        ⁢            v                          -                  P                      w            ⁢                          xe2x80x83                        ⁢            f                              )      
wherein:
Qa=Actual flow rate measured at a surface (BFPD)
Pav=Average reservoir static pressure (psi)
Pwf=Actual bottom hole flowing pressure (psi); and
wherein Qa and Pwf are either received from an external source or retrieved from the memory storage, and Pav is either generated based on data inputted from the external source, or retrieved from the memory storage.
In one embodiment consistent with the present invention, the optimum productivity index PIO is a predetermined number generated using at least one of Darcy Law and Vogel inflow equations depending on conditions of a reservoir from which the well will produce, and the optimum productivity index PIO is either retrieved from a memory storage device or received from an external source.
In one embodiment consistent with the present invention, the optimum productivity index generating step includes the step of receiving data on an average reservoir static pressure Pav and on a bubble point pressure Pb, and when the average reservoir static pressure Pav is more than the bubble point pressure Pb, the optimum productivity index PIO is automatically generated using Darcy Law according to the following expression:       P    ⁢          xe2x80x83        ⁢          I      O        =                    Q        0                    (                              P                          a              ⁢                              xe2x80x83                            ⁢              v                                -                      P                          w              ⁢                              xe2x80x83                            ⁢              f                                      )              =                  7.08        ⁢        Kh                    μ        ⁢                  xe2x80x83                ⁢                  B          0                ⁢        In        ⁢                  xe2x80x83                ⁢                  (                                                    R                e                            /                              R                w                                      -            0.5                    )                    
wherein:
K=Formation permeability in Darcies
H=Formation thickness, in ft.
Pav=Average reservoir pressure, in psi
Pwf=Bottom hole flowing pressure, in psi
xcexc=Viscosity, in Cp
Re=Outer radius of well influence, ft.
Rw=Wellbore radius, ft.
B0=Formation volume factor or volumetric factor
Q0=Flow rate (BFPD), at sand face and with no skin (S=0); and
wherein K, H, Pav, Pwf, xcexc, Re, Rw, B0, and Q0, are one of received from said external source and retrieved from said memory storage.
In another embodiment consistent with the present invention, the optimum productivity index generating step includes the step of receiving data on an average reservoir static pressure Pav and on a bubble point pressure Pb, and when the average reservoir static pressure Pav is less than the bubble point pressure Pb, the optimum productivity index PIO is automatically generated using Vogel""s equation according to the following expression:             P      ⁢              xe2x80x83            ⁢              I        O              =                  Q        max                    (                              P                          a              ⁢                              xe2x80x83                            ⁢              v                                -                      P                          w              ⁢                              xe2x80x83                            ⁢              f                                      )              ;
wherein:
Pav=Average reservoir static pressure, in psi
Pwf=Actual bottom hole flowing pressure, in psi
Qmax=Maximum flow rate liberality (BFPD); and
wherein Qmax is automatically generated according to the expression:             Q      a              Q      max        =      1    -          0.2      ⁢                        (                      P                          w              ⁢                              xe2x80x83                            ⁢              f                                )                          (                      P                          a              ⁢                              xe2x80x83                            ⁢              v                                )                      -          0.8      ⁢                                    {                          (                              P                                  w                  ⁢                                      xe2x80x83                                    ⁢                  f                                            )                        }                    2                          {                      (                          P                              a                ⁢                                  xe2x80x83                                ⁢                v                                      )                    }                    
wherein:
Qa=Actual flow rate measured at surface (BFPD)
Pav=Average reservoir static pressure (psi)
Pwf=Actual bottom hole flowing pressure (psi); and
wherein Qa and Pwf are either received from an external source or retrieved from a memory storage, and Pav is either generated based on data inputted from the external source or retrieved from the memory storage.
In another embodiment consistent with the present invention, the optimum productivity index generating step includes the step of receiving data on an average reservoir static pressure Pav, an actual bottom hole flowing pressure Pwf, and on a bubble point pressure Pb, and when the actual bottom hole flowing pressure Pwf is less than a bubble point pressure Pb, and the bubble point pressure Pb is less than the average reservoir static pressure Pav, then the optimum productivity index PIO is automatically generated using a Darcy Law modified equation defined according to the following expression:       P    ⁢          xe2x80x83        ⁢          I      O        =                    Q        0                    (                              P                          a              ⁢                              xe2x80x83                            ⁢              v                                -                      P                          w              ⁢                              xe2x80x83                            ⁢              f                                      )              =                  7.08        ⁢        Kh                    μ        ⁢                  xe2x80x83                ⁢                  B          0                ⁢        In        ⁢                  xe2x80x83                ⁢                  (                                                    R                e                            /                              R                w                                      -                          (                              0.75                +                S                            )                                )                    
wherein:
K=Formation permeability in Darcies
H=Formation thickness, in ft.
Pav=Average Reservoir Pressure, in psi
Pwf=Bottom Hole flowing Pressure, in psi
xcexc=Viscosity, in Cp
Re=Outer radius of well influence, ft.
Rw=Wellbore radius, ft.
Q0=Flow rate (BFPD), at sand face and with no Skin (S=0)
B0=Formation volume factor or volumetric factor
S=Skin factor
wherein K, H, Pav, Pwf, xcexc, Re, Rw, B0, S, and Q0, are either received from an external source and retrieved from a memory storage.
In another embodiment consistent with the present invention, when the well was producing before an operation is performed, the well productivity index ratio PIR is automatically generated as an increment to a productivity index obtained with the operation, as defined by the following expression:
PIR=(PIAxe2x88x92PIBO)/PIBO 
wherein:
PIA=Actual Productivity Index (BFPD/psi)
PIBO=Productivity Index Before the Operation (BFPD/psi); and
wherein the productivity index PIBO is automatically generated for conditions that exist before a well operation, according to the following expression:       P    ⁢          xe2x80x83        ⁢          I              B        ⁢                  xe2x80x83                ⁢        O              =                    Q        a                    (                              P                          a              ⁢                              xe2x80x83                            ⁢              v                                -                      P                          w              ⁢                              xe2x80x83                            ⁢              f                                      )              .  
In another embodiment consisting with the present invention, a computer-readable medium contains instructions that cause a data processing system having a spreadsheet program to perform a method of determining performance of a well, the method performed by the spreadsheet program including the steps of generating a well construction time ratio WCTR for the well; generating a well productivity index ratio PIR for the well; and automatically generating a well optimization index WOI for the well based on a relation between the well construction time ratio and the well productivity index ratio.
In another embodiment consistent with the present invention, a data processing system includes a memory having a spreadsheet program that generates a well construction time ratio WCTR for a well, that generates a well productivity index ratio PIR for the well, and that automatically generates a well optimization index WOI for the well based on a relation between the well construction time ratio and the well productivity index ratio to determine performance of the well; and a processor that runs the program.
In another embodiment consistent with the present invention, there exists a method in a data-processing system for determining performance of a well, the data processing system having a spreadsheet program which performs a method comprising the steps of receiving a name of the well from an external source; retrieving first data about the well from a memory storage device based on the name of the well; receiving second data about the well from the external source; generating a well construction time ratio WCTR for the well using the first data and the second data; generating a well productivity index ratio PIR for the well using the first data and the second data; and automatically generating a well optimization index WOI for the well based on a relation between the well construction time ratio and the well productivity index ratio.
In another embodiment consistent with the present invention, there exists a method in a data-processing system for determining performance of a well, the data processing system having a spreadsheet program which performs a method comprising the steps of receiving a name of the well from an external source; receiving a request to generate a well construction time ratio WCTR for the well; retrieving well construction time technical limit WCTL data on the well from a memory storage device based on the name of the well; receiving actual well construction time data WCTA on the well from an external source; automatically generating a dwell construction time ratio WCTR based on a relation between the well construction time technical limit WCTL and an actual well construction time WCTA; receiving a request to generate a well productivity index ratio PIR for the well; receiving actual productivity data on the well; generating an actual productivity index PIA based on the actual productivity data; generating an optimum productivity index PIO based on said actual productivity data and stored productivity data based on said name of the well, retrieved from the memory storage device; automatically generating the well productivity index ratio PIR based on a relation between the actual productivity index PIA and the optimum productivity index PIO; and automatically generating a well optimization index WOI for the well based on a relation between the well construction time ratio WCTR and the well productivity index ratio PIR.
In another embodiment consistent with the present invention, there exists a method of determining performance of a well, the method including the steps of generating performance data from measurements taken du ring operation of the well; generating a well construction time ratio WCTR for the well using the performance data; generating a well productivity index ratio PIR for the well using the performance data; and automatically generating a well optimization index WOI for the well based on a relation between the well construction time ratio and the well productivity index ratio.
In another embodiment consistent with the present invention, the method is performed by a data processing system.
The WOI varies from 0% (worst) to 100% (best), and can be easily used to indicate where operations may need additional attention to meet the level of performance desired (i.e., WOI as close to 100% as possible). The WOI also can be used as an indicator of the project performance trends over project time.
There has thus been outlined, rather broadly, some features consistent with the present invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features consistent with the present invention that will be described below and which will form the subject matter of the claims appended hereto.
In this respect, before explaining at least one embodiment consistent with the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. Methods and apparatuses consistent with the present invention are capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract included below, are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the methods and apparatuses consistent with the present invention.